What's wrong with network settings?

Question

Computer networks

Good afternoon.
Here is such a problem.
We installed a new router with a stable speed of 250 mb, BUT ...
Some (10% - 15% of all) sites do not respond when loading - 40 seconds then the first server response - the site is not available - and then after 5-10 seconds the browser is at 50% cases he reloads the page and it is available, in the remaining 50% of cases I force the page to be reloaded and it is available. Sometimes content loads without CSS styles.
BUT ...
If you set a limit in the card settings - 100 MB, then these problems go away, all pages respond quickly enough, BUT ...
Somehow I don’t want to have an optical line to the router forcibly restrict traffic to 100 MB ((
Maybe someone had similar experience?
Thank you!

Answer 1

I had this because of a crooked DNS server, try to force Google or Yandex DNS, and not use the default ones from the provider.

Answer 2

BUT ...
If you set a limit in the map settings - 100 MB, then these problems go away, all pages respond quickly enough ...

may indicate poor contact or incorrect crimping of the patch cord.